1. Field of the Invention
The present invention relates to a connection structure of an electronic device such as a multi-pin IC (Integrated Circuit) package, and specifically relates to a socket used for connecting to peripheral appliances or external circuits of the electronic device in order to extract signals or supply power and the like, and electronic appliances using such a socket.
2. Description of the Related Art
Conventionally, an IC package, as an example of electronic devices, has electrical power consumption of about 50 [W] at the maximum. And in order to connect such an IC package to external circuits, an IC socket equipped with a spring probe in a heat-resisting resin has been used. However, due to increased leak current in the IC package or due to the increased amount of current during operation brought by the speeding up of test frequency, when heat generation higher than 100 [W] is performed, heat generation in probes becomes an issue. Furthermore, with the widened data bus width, the ratio of signal pins tend to increase while the ratio of power pins (V/G) tend to decrease, which requires an IC socket that can support a large current.
By the way, a spring probe disposed in an IC socket includes, for example, a pair of plungers to bring into contact with the electrode pads, and has a tube structure to make electrical connection by providing a spring or the like between each of the plungers and by pressing the plungers to connect to the electrode pads. In the IC socket having such a structure, contact resistance comes with the structure and the contact resistance generates heat.
With regard to such heat generation in IC sockets, among conventional patent documents, there is one providing a heat sink in which a cooling fan is embedded in an IC socket (e.g., Japanese Patent Application Laid-Open Publication No. H10 (1998)-294582 (paragraph No. 0023, FIG. 1, etc.)); and one providing heat insulation and cooling structure of probes (e.g., Japanese Patent Application Laid-Open Publication No. 2000-241454 (paragraph No. 0030, FIG. 1, etc.)).
By the way, since a probe disposed between the electrode pads constitute a current path, contact portions (ohm contact) of plungers and a tube that supports the plungers in the probe are included in the current path, therefore resistance component in the contact portions causes heat generation. In such a structure that has a ball between the plunger and the spring, the contact portions of the ball and the plunger, and the contact portions of the ball and the tube constitute a part of the current path, so that the resistance component in these contact portions cause heat generation as well. Even though parts of the plunger, the tube, or the like are made of good conductive materials, when a current “i” flows through a contact resistance “r” existing in the contact portions, a heat “i2r” is generated. Because of this heat generation, restriction is placed on permissible current.
Further, with regard to relationship between the distance of the IC package and the spring probe, and internal resistance, although resistance is small in peripheral portions of the IC package because the distance from the spring probe is short; whereas resistance becomes large in the central portion side of the IC package because the distance from the spring probe is long. Therefore, when a large current flows by the power supply in the IC package, a potential difference arises between the central portions of the package and the spring probe contacting the peripheral portions of the package, which causes a voltage drop.
Therefore, it becomes necessary to secure permissible current as well as to reduce voltage drop in a current path in order to enable a large current flowing in a socket. And in order to secure permissible current, it is necessary to suppress high temperature by enhancing heatsinking of probes.
None of the above-described patent documents disclose nor suggest such issues at all, and there is no descriptions or suggestions about the solution.